Hitherto, transparent conductive film has typically been formed of ITO, which contains indium, a rare metal. Thus, there has been proposed a zinc-oxide-based conductive material, which is an alternative transparent conductive material to ITO.
In one known embodiment of zinc oxide, a conductive film containing zinc oxide is formed on a transparent substrate containing olefin resin, to thereby produce a transparent conductive film stacked structure having high optical transmittance (see, for example, Patent Document 1). The transparent conductive film stacked structure disclosed in Patent Document 1 has, in some cases, a resistivity which is not sufficiently low, and the sheet resistivity of the stacked structure deteriorates under high-moisture and high-temperature conditions, as compared with ITO.
In the case of transparent conductive film containing gallium oxide and zinc oxide, the deterioration of sheet resistivity thereof under high-moisture and high-temperature conditions is known to be suitably controlled by considerably increasing the amount of gallium oxide (dopant) and increasing the film thickness to 400 nm (see, for example, Non-Patent Document 1). When the countermeasures are employed, productivity becomes very poor due to formation of transparent conductive film having a film thickness of 400 nm, and the considerable increase in gallium oxide (dopant) amount makes the cost non-practical.